Background: Previous studies showed that gait deficits are exacerbated during addition of dual motor or cognitive tasks in patients with Parkinson's disease (PD). However, no study has reported the effect of naming an object that a patients saw while walking in PD patients. Visual cue was found to increase the stride length, but not gait velocity in PD patients under dual cognitive-walking task condition. A previous study reported that when combined auditory and visual cues were given before sit-to-stand, the performance in PD patients was enhanced. Whether preparatory audio-visual (AV) cues could facilitate walking under dual cognitive-walking task condition in PD patients is unknown. Objectives: This study aimed to examine the effect of adding a cognitive task to walking on gait performance; and to determine whether preparatory AV cues could enhance walking under dual cognitive-walking task condition in PD patients. Methods: This study composed of a pilot and two inter-related main studies. The pilot study established the reliability of the methodology. In Study 1, twenty-two PD patients and 15 healthy subjects were instructed to: (1) walk at their natural pace (Walk₀); (2) name the object on the computer screen while they walked (Walk naming object) and (3) say out tne serial subtractions of three from 100 while they walked (Walk calculation). In Study 2, fifteen PD patients and 13 control subjects randomly walked under 4 conditions (AV-and non-cued). The AV cues were simulated road-crossing traffic light and sound, which were presented once to subjects before walking so they could estimate the walking time. Subjects had to walk while (1) naming the object on the computer screen (Walk naming object); (2) saying out the serial subtractions of three from 100 (Walk calculation); (3) naming the object on the computer screen with the addition of AV cues (AV naming object); (4) saying out the serial subtractions of three from 100 with the addition of AV cues (AV calculation). Gait velocity, stride length, cadence and the number of correct answers for the cognitive tasks were recorded.Results and discussion: Excellent ICCs (>0.90) were found in all gait parameters in both subject groups, indicating that the methodology was reliable. For Study 1, PD patients walked with significantly slower gait velocity (by 15.3%) and shorter stride length (by 10.1%) than control subjects under Walk0. When either concurrent task of "naming object" or "calculation" was added to walking, a significant group*task interactions was found in gait velocity and stride length. PD subjects significantly decreased gait velocity (by 17.4%, 25.8%), stride length (by 13.5%, 15.0%) and cadence (by 4.5%, 12.1%) in Walk naming object and Walk calculation than Walk₀(p<0.05). The difference between Walk naming object and Walk calculation was insignificant. In contrast, control subjects maintained their performance in Walk naming object as those of Walk 0, but significantly reduced gait velocity and cadence in Walk calculation. These findings indicate that distraction of attention such as simple object naming or calculation could affect walking performance in PD patients. Therefore, walking appeared to demand more attention in these patients. In Study 2, PD subjects significantly increased gait velocity (by 12.8%, 17.4%), stride length (by 7.6%, 8.2%) and cadence (by 4.7%, 9.2%) in AV naming object and AV calculation than non-cued conditions (p<0.01). In control group, the addition of AV cues also produced significant but less strong and widespread effects on the various gait parameters. The stronger and more widespread positive outcomes in PD patients suggest that AV cues could have facilitated the motor preparatory process and heightened the attention level of these subjects. Therefore they were better able to complete their walk within the pre-set time, leading to increased stride length, gait velocity and cadence. Conclusion: When a concurrent cognitive task (naming object or calculation) was added to walking, PD patients showed deterioration in all gait parameters. Our findings imply that PD patients require more attention to walk than normal controls. Provision of preparatory AV cues enhanced all gait performance under the two dual cognitive-walking task conditions examined. The positive findings from this study provide scientific evidence for the use of AV cues in the facilitation of dual cognitive-walking in PD subjects.

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